The present invention relates to a digital copier having a facsimile transmission and reception capability.
A recent achievement in the imaging art is a digital copier which is the combination of a document reader which digitally reads the image of an original document and laser printer or like page printer which records images page by page with predetermined resolution. This kind of copier has a capability of reproducing images in an edited condition and a capability of processing images themselves as well as a usual copying capability. Further, a digital copier may serve as an output unit of a personal computer or like data processing device for producing hard copies or may even by provided with a communication function to serve as a facsimile terminal.
A predominant type of facsimile apparatus is equipped with a paper in the form of a roll for recording received data and accommodates only a single roll of a particular size at a time. Assuming that this type of facsimile apparatus is loaded with a paper of A4 size only, received image size may be successfully printed out on the paper if the image size is A4, but they have to be reduced before printed out if the image size is B4. Conversely, when the paper loaded in the facsimile apparatus is of B4 size, received images of A4 and B4 sizes may be recorded by .times.1 magnification. In this case, however, recording a received image of A4 size on the B4 paper by .times.1 magnification would leave a substantial blank area on the paper which is undesirable from the filing standpoint.
In light of this, there has been proposed a facsimile apparatus which can be loaded with papers of a plurality of sizes (usually two sizes) at a time. When this kind of apparatus is loaded with papers of A4 and B4 sizes by way of example, a received image of A4 or smaller size is printed out on the A4 paper by .times.1 magnification, a received image of B4 size is printed out on the B4 paper by .times.1 magnification, and a received image of a size larger than B4 is printed out on the B4 paper in a reduced scale. When a person desires to receive images with the A4 paper only, he or she may not mount the B4 paper.
Generally, a digital copier includes a photoelectric transducer such as one implemented with charge coupled devices (CCD) which is adapted to read a document laid on a glass platen. An image signal outputted by the transducer drives laser optics or like digital optics, whereby a photoconductive drum is exposed imagewise to reproduce the document by electrophotography. When the image signal is applied to a MODEM in place of the optics, the copier turns into a facsimile apparatus. In a receive mode, an image signal applied to the MODEM is fed to the optics. A digital copier, therefore, is capable of serving both of the copying function and the facsimile data receiving and transmitting function if provided with a MODEM and some signal switching means. A digital copier which is originally a copier is provided with a plurality of cassettes each being loaded with cut papers of a different size and removable from a housing of the copier. The housing is formed with a plurality of openings each being capable of accommodating any of the cassettes with no regard to the paper size.
Now, a facsimile apparatus compresses data to be transmitted. When only papers of A4 size are available at a receive station, the facsimile apparatus cannot transmit an image of B4 size unless it performs reduction in addition to compression. Although an image may be transmitted without being reduced and printed out at a receive station in a reduced scale, transmitting an image after reducing it at a transmit station halves the transmission time compared to transmitting it without reduction. Specifically, should only the papers of size A4 be available at the receive station, the image would eventually be reduced at the receive station. Another possible approach is transmitting all the images of sizes larger than A4 after reducing them to A4 so that they may be printed out in an enlarged scale at a receive station. This approach, however, has a drawback that the image quality is degraded because an image is reduced and then enlarged. To cope with this problem, according to the CCITT protocol, a receive station informs a transmit station of a paper size which is available there so that the transmit station may select a .times.1 magnification mode or a reduction mode on the basis of the paper size reported and the image size to be transmitted. The previously mentioned type of apparatus which accommodates only a single paper size sends size data by protocol, and the apparatus with which two different paper sizes are usable at a time sends one of the paper sizes which is larger than the other. Assuming that the apparatus is loaded with papers of A4 and B4 sizes and that the B4 size is delivered as size data, then a transmit station sends images smaller than A4 size by .times.1 magnification while a receive satin prints out images smaller than A4 on the A4 papers and B4 images on the B4 papers.
In the case that the apparatus which is originally designed as a copier is provided with a MODEM and other extra elements to bifunctional as a facsimile terminal, the cassettes, i.e., papers loaded in the apparatus are initially prepared for a copying purpose. In a receive mode, so long as the largest paper size is transmitted as size data to a transmit station, images of all the sizes can be received by .times.1 magnification only if a cassette loaded with A3 papers is mounted in any of the openings of the copier housing. This, however, is inconvenient for those users who desire to uniformize the size of received images for easy filing and other purposes, as stated earlier. For example, when a user intends to limit the size of received images to A4, the user has to remove the other cassettes which are loaded with B4 and A3 papers in the event of facsimile reception. Specifically, every time the user desires to copy an original document on a paper of B4 of A3 size, he or she has to mount the B4 or A3 cassette and then remove it after copying. This is because the time of reception of facsimile data cannot be predicted. Indeed, facsimile data may be received while a copying operation is under way with papers of B4 size (they can be received because the MODEM is idle during copying operation). In such a condition, the B4 size which is not the true largest size is sent to a transmit station as size data.